Embryonic stem cells (ES cells) have pluripotency to differentiate into various tissue cells. Various researches have been made to utilize this potency for application to the field of so-called regeneration medical care, namely, repairing cells lost due to diseases, accidents or the like and recovering the tissues (see Patent document 1 for example).
ES cells have diversity to allow differentiation into various cells. It involves correlation among cells, and one example thereof is formation of a cell mass called an embryonic body (EB). This cell mass is formed by suspension culture of ES cells, iPS cells or the like. After culturing for about 2 weeks in a state where the cell mass is formed, differentiation into various cell types can be observed. Therefore, the embryonic body is used as a general method to examine pluripotency of cells.
A method used most widely for culturing ES cells in a suspended state is a hanging drop culture. The hanging drop culture is a method of culturing cells in a culture solution hanging like a water drop. However, this method causes some problems, for example, the success rate in embryonic body formation is low, microscopic observation is impossible, and the operations are arduous. For solving these problems, for example, a culture vessel provided with a water-insoluble cured coating film formed on the inner surface of the vessel by curing a water-soluble resin coating film is proposed (see Patent document 2 for example).
The above-mentioned Patent document 1 (JP 2008-99662) and Patent document 2 (JP 2008-178367) are incorporated herein by reference.